Cracking in the presence of a volatile acid



CRACKING IN THE PRESENCE OF A VOLATILE ACID Jack H. Krause, Media, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware N Drawing. Filed June 3, 1957, Ser. No. 662,984

1 Claim. (Cl. 208-115) over a suitable contact material such as alumina to pro vide a high severity of cracking. Relatively large amounts of acidic accelerator such as 1 or 2% by weight of the hydrocarbon have been employed in such procedures. Volatile acids have generally favored cracking reactions forming relatively large amounts of gas and coke, with poor selectivity for forming large proportions of gasoline (liquids boiling below 400 C.). Hence, gaseous acidic reagents as accelerators for hydrocarbon have been favored when great severity of cracking was important enough to compensate for the poor selectivity of such cracking procedure. In the reforming of gasoline in the presence of a platinum catalyst, halide addition has been employed to enhance the cracking activity of the halide combined with the aluminaceous carrier. in such reforming operations, great care has been exercised to minimize the presence of steam. In fact, steam and hydrogen halide have been treated as opposites, and steam has been employed to reduce the halide content of the platinum alumina catalyst whenever excessive amounts of halide have been deposited on the catalyst during the reforming with halide addition.

Substantially all cracking operations have been conducted making use of hydrocarbons which were readily converted to vapor. Great diffieulty has been encountered in attempts to prepare useful products from residual hydrocarbon.

Crude petroleum contains hydrocarbons of a variety of boiling points. The more volatile components are removed by the conventional distillation of crude petroleum. Such distillation also results, in the formation of a product designated as residuum, from which the volatile components are not distillable at a commercially attractive rate at atmospheric pressure. Various efforts have been made to crack such residuum in order to prepare gasoline, distillate, fuel oil and/ or other products more valuable than residuum. In such cracking of residuum, steam has sometimes been employed to aid in the removal of the vapors of the liquid products from the cracking zone.

Prior art technologists may have concluded that, because steam apparently had the opposite effect of a volatile acid, the combination of steam and violatile acid would provide no useful purpose in the cracking of residuum, Surprisingly, however, the present invention involves the discovery that the combination of steam and volatile acid in a cracking zone for the cracking of residuum brings about a greater selectivity in the cracking reaction, whereby significantly greater amounts of liquid hydrocarbons boiling below 400 F. are obtained than Patented Sept. 6, 1960 would be obtained under comparable cracking conditions without such combination.

In accordance with the present invention volatilizable components are distilled from a crude petroleum, thereby leaving a residuum, and a steam of the residuum is injected into a cracking zone containing solid contact material and also steam and a minor amount of a volatile acidic agent are injected into said cracking zone while maintaining the temperature and pressure of the cracking zone at cracking conditions and there is withdrawn from the cracking zone a mixture comprising the volatile acidic agent, steam and hydrocarbon vapors including larger amounts of vapors of liquid hydrocarbons boiling below 400 'F. than would be obtained in the absence of said volatile acidic agent. In certain embodiments of the invention: the volatilizable components are distilled from crude petroleum at atmospheric pressure at temperatures and rates below those at which there is signi-fican-t cracking of the liquid being distilled; and/or bottoms residual fraction constitutes at least 1% but not more than 15% by weight of the crude petroleum; and/ or the amount of volatile acid is less than 1000 parts per million but more than 1 part per million, based upon the weight of the hydrocarbon charge; and/or the volatile acid is hydrogen chloride; and/or approximately 720 parts per million of hydrogen chloride serve as the volatile acid; and/or the contact material is a gravitating bed of coke granules; and/or the contact material is kaolin cracking catalyst.

Additional clarification of the technical subject matter is achieved satisfactorily by reference to a plurality of examples.

EXAMPLE I The crude petroleum is subjected to fractional distillation to prepare a gasoline fraction boiling below 400 F., a gas oil fraction boiling between 400 F. and 850 F. and a residuum constituting substantially 14% by weight of the initial crude petroleum. This residuum is heated and sprayed onto hot granules of petroleum coke gravitating as a non-turbulent bed through a cracking zone. Near the bottom of the cracking zone, steam is injected upwardly to promote the removal of volatile vapors from the carbonaceous contact material. The amount of steam introduced into the cracking zone per hour is approximately 20% by weight of the amount or" residuum fed to the cracking zone per hour. The cracking zone is maintained at atmospheric pressure and at a temperature of 875 F. Volatile products together with steam are withdrawn from the top of the cracking zone. The carbonaceous material deposited on the gravitating particles of coke brings about an increase in the quantity of petroleum coke, and an appropriate amount of such particles is withdrawn as a product of the reaction.

EXAMPLE II Residuum hydrocarbons are subjected tosteam cracking in the presence of gravitating bed of petroleum coke in a manner very similar to that of Example I, with the modification that an amount of hydrogen chloride corresponding to 50 parts per million parts of residuum are introduced with the steam. Surprisingly, the quantity of liquid hydrocarbon product boiling below 400 F. is significantly increased without any great increase in the quantity of normally gaseous hydrocarbons, thus, indicating that the hydrogen chloride serves to enhance the selectivity of the conversion conditions for preferential formation of liquid hydrocarbons boiling below 400 F. Such increase in selectivity is of greater value to the marketer of gasoline than would be a slight improvement in the activity of the catalyst, inasmuch as the price difference between gasoline and residuum is greater than the price difference between residuum and and coke.

EXAMPLE III A laboratory cracking unit contains a fixed bed of kaolin catalyst granules. A 14% bottoms fraction is subjected to steam cracking in the unit with and without the addition of 720 parts per million of hydrogen chloride based upon the weight of residuum charged to the unit. Using the same cracking conditions, except for the hydrogen chloride additive, the same residiuum provided products as indicated in the following table:

Such data indicate that the hydrogen chloride in the presence of steam and in the presence of the catalyst granules serves to enhance the selectivity of the crack ing of the residuum. Although such data show that the activity of the catalyst is slightly less in the presence of the hydrogen chloride accelerator, but the improvement in selectivity is significantly more valuable than such decrease in activity.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore, only such limitations should be imposed as are indicated in the appended claim.

What is claimed is:

The method of preparing useful products from the residuum remaining after the distillation of at least 85% by weight of a crude petroleum which method comprises the steps of: providing a catalytic cracking zone containing granules of kaolin cracking catalyst; introducing into said cracking zone a mixture consisting essentially of preheated residuum, steam constituting approximately 20% by weight of the residuum, and hydrogen chloride in a quantity constituting approximately 720 parts per million of the residuum; maintaining cracking conditions in the catalytic cracking zone, thereby converting the residuum to normally gaseous hydrocarbons, liquid hydrocarbons boiling below 400 -F., liquid hydrocarbons boiling above 400 F. but volatilized from the kaolin catalyst granules, and carbonaceous deposits on the kaolin catalyst granules, said conversion producing significantly more liquid hydrocarbons boiling below 400 F. than would result other than in the presence of said quantity of hydrogen chloride because of the selectivity enhancing activity of said quantity of hydrogen chloride in the presence of steam and kaolin in the catalytic zone; withdrawing as eifiuent a mixture of steam, hydrogen chloride, and volatilized hydrocarbons from the catalytic cracking zone; and recovering liquid hydrocarbons from such efiluent.

References Cited in the file of this patent UNITED STATES PATENTS 1,235,523 McAfee July 31, 1917 1,805,616 Egloff et al. May 19, 1931 2,001,444 Zotos a May 14, 1935 2,737,475 Voorhies Mar. 6, 1956 2,859,175 Adams et al. Nov. 4, 1958 FOREIGN PATENTS 283,105 Great Britain Dec. 6, 1928 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Jack He Krause or appears in the-printed specification t the said Letters It is hereby certified that err ng correction and tha of the above numbered patent requiri Patent should read as corrected below.

second occurrence;

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t cracking n Column 3, line 1 "catalytic" iIlSGI column 4 line 20,, after (I sealed this 11th day of April 1961,

Signed an (SEAL) Attest:

E w. IDE

RNEST H R ARTHUR w. CROCKER Attesting Oificer Acting Commissioner of Patent: 

